Marine radiocarbon reservoir age simulations for the past 50,000years

Radiocarbon (C-14) dating calibration for the last glacial period largely relies on cross-dated marine C-14 records. However, marine reservoirs are isotopically depleted with respect to the atmosphere and therefore have to be corrected by the Marine Radiocarbon Ages of surface waters (MRAs), whose temporal variabilities are largely unknown. Here we present simulations of the spatial and temporal variability in MRAs using a three-dimensional ocean circulation model covering the past 50,000years. Our simulations are compared to reconstructions of past surface ocean C-14. Running the model with different climatic boundary conditions, we find that low-latitude to midlatitude MRAs have varied between 400 and 1200 (14)Cyears, with values of about 780 (14)Cyears at the Last Glacial Maximum. Reservoir ages exceeding 2000 (14)Cyears are simulated in the polar oceans. Our simulation results can be used as first-order approximation of the MRA variability in future radiocarbon calibration efforts.